1. Field
The various embodiments described herein pertain generally to an atomic layer etching method for graphene, including adsorbing reactive radicals onto a surface of the graphene and irradiating an energy source to the graphene on which the reactive radicals are adsorbed.
2. Description of Related Art
Exfoliated graphene has excellent physical and electrical characteristics. Due to these advantages, research on graphene has been actively conducted. In conventional methods of producing an exfoliated graphene, however, adjustment and positioning of graphene layers have been impossible. Thus, the exfoliated graphene produced by conventional methods has a problem in that it is less suitable to be commercialized for various purposes.
In this regard, recently, graphene produced by a chemical vapor deposition (CVD) method is attracting attention. The graphene produced by the CVD method has physical and electrical characteristics very similar to those of the exfoliated graphene produced by conventional methods and can be deposited on a wafer scale. Thus, research for the purposes of applying the graphene produced by the CVD method to a channel device or the like has been conducted in various ways.
However, in case of a device having only a channel portion of which is formed of graphene produced by the CVD method or the like, there may occur a contact failure between the graphene of the channel portion and a metal of source/drain electrodes. A metal [Au (25 nm)/Ti (10 nm)] electrode usually used as the source/drain electrodes in recent days has a very high contact resistance ranging from about 450Ω to about 800Ω against the graphene. Thus, degradation of a device characteristic may be caused. As an example of this conventional technique, Korean Patent Publication No. 10-2012-0048241 titled “Semiconductor device including graphene and manufacturing method thereof” describes a device including metal source/drain electrodes and a graphene channel.
Meanwhile, in order to solve the problems of the conventional methods of producing an exfoliated graphene, various new methods for etching an atomic layer of graphene have been under development. By way of example, an atomic layer etching method for graphene using HeIM (Helium Ion beam Microscopy), and an atomic layer etching method for graphene using O2 plasma, etc., have been reported. According to these atomic layer etching methods for graphene, however, adjusting a graphene layer is not easy. Particularly, the atomic layer etching method for graphene using O2 plasma has a drawback in that oxygen may remain at the edge of the graphene after the graphene is etched, thus affecting characteristics of the graphene.